View metadata, citation and similar papers at core.ac.uk brought to you by CORE

provided by International Institute for Science, Technology and Education (IISTE): E-Journals

Jordan Journal of Civil Engineering, Volume 5, No. 2, 2011

Influence of Silica Fume, Fly Ash, Super Pozz and High Slag Cement on Water Permeability and Strength of Concrete

A. A. Elsayed

Modern Academy for Engineering and Technology , Cairo, Egypt

ABSTRACT

In this study, effects of mineral admixtures on water permeability and compressive strength of concretes containing silica fume (SF), fly ash (FA) and super pozz (SP) were experimentally investigated. Permeability of concrete was determined through DIN 1048 (Part 5). The research variables included cement type, ordinary Portland cement (OPC) or high slag cement (HSC), and mineral admixtures content was used as a partial cement replacement. They were incorporated into concrete at the levels of 5%, 10% and 15% for silica fume and 10%, 20% and 30% for fly ash or super pozz by weight of cement. Water-cement ratio of 0.40 was used and tests were carried out at 28 days. From the tests, the lowest measured water permeability values were for the 10% super pozz and 10% silica fume or 20% fly ash mixes. The highest compressive strength of concretes determined was for 10% silica fume mix with ordinary Portland cement and was reduced with the increase in the replacement ratios for other mineral admixtures than ordinary Portland cement concrete.

The main objective of this research was to determine the water permeability and compressive strength of concrete containing silica fume, fly ash, super pozz and high slag cement to achieve the best concrete mixture having lowest permeability. The results were compared to those of the control concrete; ordinary Portland cement concrete without admixtures. The optimum cement replacement by FA, SP and SF in this experiment was 10% SP. The knowledge on the strength and permeability of concrete containing silica fume, fly ash, super pozz and high slag cement could be beneficial in the utilization of these waste materials in concrete work, especially on the topic of durability.

KEYWORDS: Permeability, Strength of concrete, Silica fume (SF), Fly ash (FA), Super pozz (SP), high slag cement (HSC).

INTRODUCTION produced from burning of powdered coal in power plants. Silica fume is also known as micro-silica, It is known that permeability controls deterioration volatilized silica or condensed silica fume. It is a by- of concrete in aggressive environments (Alexander and product of silicon metal and ferrosilicon alloy Magee, 1999), because the processes of such production. The material is a very fine powder with deterioration as carbonation, chloride attack and sulfates spherical particles about 100 times smaller in size than attack are governed by the fluid transportation in Portland cement or fly ash. Slag is a by-product of the concrete. Fillers and pozzolanic materials are introduced production of steel. During production, liquid slag is to improve the strength and other properties of concrete rapidly quenched from a high temperature by immersion for necessary conditions. Fly ash and super pozz are in water (Mehta, 1993). The slag is a glassy, granular, non-metallic product that consists “essentially of Accepted for Publication on 15/4/2011. silicates and aluminosilicates of calcium and other

- 245 - © 2011 JUST. All Rights Reserved. Influence of Silica Fume,… A. A. Elsayed bases” (Klieger and Lamond, 1994). It is also known as the topic of durability. granulated blast furnace slag (GBFS). The aim of this research was to study water permeability and EXPERIMENTAL PROGRAM compressive strength of concrete containing silica fume, fly ash, super pozz and high slag cement to achieve the Materials best concrete mixture having lowest permeability. The results were compared to those of the control concrete; Cement and Cement Replacement Materials ordinary Portland cement concrete without admixtures. Ordinary Portland Cement The knowledge on the strength and permeability of Ordinary Portland cement used was provided from concrete containing silica fume, fly ash, super pozz and Tourah-factory. The approximate mineral composition high slag cement could be beneficial in the utilization of of the used cement is shown in Table (1) (Helmuth, these waste materials in concrete work, especially on 1987).

Table 1: Typical composition of ordinary Portland cement

constituents C3S C2S C3A C4AF CSH2 Total Percent % 50 25 12 8 3.5 98.5

High Slag Cement When used in concrete, slag provides the following Slag is a by-product of the production of steel. benefits (Lewis, 1985): During production, liquid slag is rapidly quenched from a high temperature by immersion in water (Mehta, • High ultimate strength with low early strength, 1993). The slag is a glassy, granular, non-metallic • High ratio of flexural to compressive strength, product that consists “essentially of calcium silicates • Resistance to sulfates and seawater, and aluminosilicates of calcium and other bases” • Improved alkali-silica reaction resistance, (Klieger and Lamond, 1994). It is also known as • Low heat of hydration, granulated blast furnace slag (GBFS). Slag, in addition • Decreased porosity and permeability, and to pozzolanic properties, and unlike Class F fly ash and • Better finish and lighter color. silica fume, also has cementitious properties. With regard to strength, there are three grades of slag: Grade Slag is also known for improved workability and 80, Grade 100 and Grade 120. Each number lower water requirement (Fulton, 1974). Slag hydration corresponds to a minimum 28-day compressive strength is significantly influenced by temperature: hydration is ratio of a mortar cube made with only Portland cement accelerated at higher temperatures and retarded at lower and a mortar cube made with 50% Portland cement and ones, when compared to Portland cement hydration. 50% slag. Because of cementitious properties, particles This may lead to differences between the strength of smaller than 10 m (m stands for micron) contribute to concrete in the field and the laboratory specimens early strength, while particles larger than 10 m and (Mehta, 1993). The chemical analysis and physical smaller than 45 m contribute to later strength. Since properties of slag are presented in Table (2) (Sobolev particles greater than 45 m are difficult to hydrate, slag and Batrakov, 2007). is mostly pulverized to particles with a diameter less than 45 m (Mehta, 1993).

- 246 - Jordan Journal of Civil Engineering, Volume 5, No. 2, 2011

Table 2: Chemical analysis and • Lower cost concrete, physical properties of slag • Improved resistance to sulfate attack, • Improved resistance to alkali-silica reaction, Analysis and properties Mass % • Higher long-term strength,

SiO2 39.0 • Opportunity for higher strength concrete,

Al2O3 8.7 • Equal or increased freeze thaw durability,

Fe2O3 0.5 • Lower shrinkage characteristics, and CaO 41.3 • Lower porosity and improved impermeability. MgO 8.5 Table 3: Chemical analysis and physical properties Na2O 0.15 of fly ash K2O 0.21 Chemical Analysis Mass % Mass % SO3 0.74 Loss on ignition (LOI) 0.52 Silica (SiO2) 47.0-55.0 Specific Surface Area (cm2/g) 7000 Aluminium (Al2O3) 25.0-35.0 Specific gravity 2.92 Iron (Fe2O3) 3.0-4.0 Manganese (Mn2O3) 0.1-0.2 Fly Ash Calcium (CaO) 4.0-10.0 Fly ashes are by-products produced during Magnesium (MgO) 1.0-2.5 combustion of powdered coal in power plants. A Phosphorus (P2O5) 0.5-1.0 summary of the properties and chemical composition of Potassium (K2O) 0.5-1.0 different fly ashes was presented by Helmuth (Mindes Sodium (Na2O) 0.2-0.8 and Young). In general, depending on the chemical Titanium (TiO2) 1.0-0.5 composition, fly ash can be classified as Class F or Sulphur (SO3) 0.1-0.5 Class C. Class C fly ash has higher amount of CaO, so it Loss on Ignition (LOI) 0.5-2.0 possesses more cementing characteristics and is less Specific Surface Area (cm2/g) 8500 pozzolanic than Class F fly ash. ASTM 618 states that Specific gravity 2.6 Class F fly ash is “normally produced from burning anthracite or bituminous coal”, while Class C fly ash is Super Pozz “normally produced from lignite and subbituminous As can be seen in the chemical composition and coal” (ASTM). Class F fly ash is mostly composed of physical characteristics listed in Table 4, super pozz is silicate glass containing aluminum, iron and alkalies. an extremely fine, light colored powder composed The particles are in the form of solid spheres with sizes primarily of amorphous calcium-silicates and ranging from less than 1 m to 100 m and an average aluminates. From its chemical analysis, super pozz will diameter of 20 m (Mehta, 1993). At least 70% of the meet the Class F fly ash requirement of BS 3892, but chemical composition is made up of SiO2, Al2O3 and physically the product is unique with regards to its Fe2O3 (Flieger and Lamond, 1994). The chemical particle size distribution. The D99 value is 25 microns, analysis and physical properties of fly ash are shown in the particle size below which 99% of the particles are to Table (3). be found. Figure 1 illustrates the comparative particle The benefits of using fly ash in concrete include the size distribution analysis. The chemical analysis and following (Klieger and Lamond, 1994): physical properties of super pozz are shown in Table • Improved workability, (4). • Lower heat of hydration,

- 247 - Influence of Silica Fume,… A. A. Elsayed

Table 4: Chemical analysis and physical properties Table 5: Chemical analysis and physical properties of super pozz of silica fume

Analysis and properties Mass % Analysis and properties Mass %

SiO2 53.5 SiO2 90.2

Al2O3 34.3 Al2O3 1.7

CaO 4.4 Fe2O3 0.4

Fe2O3 3.6 CaO 2.1

K2O 0.8 MgO 1.7

MgO 1.0 Na2O 0.7

Loss On Ignition (LOI) < 1.0 K2O 0.7 2 Specific Surface Area (cm /g) 13000 SO3 0.5 Specific gravity 2.20 Loss on ignition (LOI) 2.5 2 Specific Surface Area (cm /g) 200000 Silica Fume Specific gravity 2.21 Silica fume is also known as micro-silica, volatilized silica or condensed silica fume. It is a by-product of Aggregates silicon metal and ferrosilicon alloy production. The material is a very fine powder with spherical particles Natural sand with a fineness modulus of 2.32 and a about 100 times smaller in size than those of Portland specific gravity of 2.65 was used as fine aggregate. cement or fly ash. The diameters range from 0.02 to 0.5 Crushed dolomite stone with a nominal maximum size m with an average of 0.1 m. Silica fume contains 85 to of 28 mm and a specific gravity of 2.70 was used as 95% noncrystalline silicon dioxide. The first application coarse aggregate. Sieve analysis tests were carried out of silica fume in the United States was conducted in on the used aggregates and the results are listed in Table Kentucky in 1982 (Klieger and Lamond, 1994). The use (6) and Table (7). of silica fume will make concrete with the following properties (Sobolev and Batrakov, 2007): Table 6: Sieve analysis test results of sand • Low heat of hydration, • Retarded alkali-aggregate reaction, Fine aggregate • Reduced freeze-thaw damage and water erosion, Sieve size (mm) passing % retained % • High strength, • Increased sulfate resistance, and 9.5 100 0 • Reduced permeability. 4.75 98.6 1.4 2.36 96.52 3.48 Silica fume is also known for creating problems in 1.18 90. 72 9.28 handling and cracking related to its small particle sizes 0.6 69.82 30.18 and increased water requirement. 0.3 12.42 87.58 The chemical analysis and physical properties of 0.177 0 100 silica fume are shown in Table (5).

- 248 - Jordan Journal of Civil Engineering, Volume 5, No. 2, 2011

Table 7: Sieve analysis test results of gravel Water Coarse aggregate Clean drinking fresh water, free from impurities was

used in the mixes. Water-cement ratio was 0.40 by Sieve size (mm) passing % retained % weight. 38.1 100 0 28 95.57 4.43 Concrete Mixtures 19 48.83 51.17 14 13.43 86.57 OPC was partially replaced by silica fume (SF) at 9.5 1.13 98.87 5%, 10% and 15%, whereas fly ash (FA) and super pozz 4.75 0.13 99.87 (SP) replaced OPC at 10%, 20% and 30%, by weight of 2.36 0.03 99.97 binder. The binder content of concrete was set constant 3 1.18 0 100 at 400 kg/m and mix proportions of concrete are 0.6 0 100 presented in Tables (8, 9 and 10). The amounts of water 0.3 0 100 and coarse aggregate in all concrete mixtures were constant. 0.177 0 100

Table 8: Mixture proportions for fly ash mixes Mixture Designation Materials (Kg/m3) 100% 0PC 10 % FA 20 % FA 30 % FA Ordinary Portland Cement 400 360 320 280 Coarse Aggregate 1212.34 1212.34 1212.34 1212.34 Fine Aggregate 681.94 675.6 669.3 662.9 Water 160 160 160 160 HRWR (L/m3) 8 8 8 8 Fly Ash - 40 80 120 Calculated Unit Wt 2462 2456 2450 2443 w/c 0.4 0.4 0.4 0.4

Table 9: Mixture proportions for super pozz mixes Mixture Designation Materials (Kg/m3) 100% OPC 10 % SP 20 % SP 30% SP Ordinary Portland Cement 400 360 320 280 Coarse Aggregate 1212.34 1212.34 1212.34 1212.34 Fine Aggregate 681.94 673.7 665.5 657.2 Water 160 160 160 160 HRWR (L/m3) 8 8 8 8 Super-Pozz - 40 80 120 Calculated Unit Wt 2462 2454 2445 2437 w/c 0.4 0.4 0.4 0.4

- 249 - Influence of Silica Fume,… A. A. Elsayed

Table 10: Mixture proportions for silica fume mixes

Mixture Designation Materials (Kg/m3) 100% HSC 5% SF 10% SF 15% SF Ordinary Portland Cement 400 380 360 340 Coarse Aggregate 1204.4 1212.34 1212.34 1212.34 Fine Aggregate 677.5 674.11 666.28 658.46 Water 160 160 160 160 HRWR (L/m3) 8 8 8 8 Silica Fume - 20 40 60 Calculated Unit Wt 2450 2455 2447 2439 w/c 0.4 0.4 0.4 0.4

Table 11: Results of compressive strength and max. penetration water depth

compressive strength at 28 days max. penetration water depth mixes value(kg/cm2) % of control mix value (mm) % of control mix OPC (control mix) 465 100 27 100 HSC 517 111 25 93 10FA 435 94 23 85 20%FA 414 89 15 56 30%FA 370 80 28 104 10%SP 486 105 10 37 20%SP 422 91 22 82 30%SP 386 83 30 111 5 % SF 504 108 20 74 10%SF 643 138 12 44 15%SF 533 115 16 59

TESTING terminated and the specimen rejected. It shall be checked whether and when the unexposed specimen Water Permeability faces show signs of water permeation. Immediately after The permeability of concrete was determined the pressure has been released, the specimen shall be through DIN 1048 (Part 5). Permeability test gives a removed and split down the centre, with the face which measure of the resistance of concrete against the was exposed to water facing down. When the split faces penetration of water exerting pressure. It shall normally show signs of drying (after about 5 to 10 minutes), the be carried out when the age of the concrete is 28 to 35 maximum depth of penetration in the direction of slab days. A concrete specimen shall be exposed either from thickness, shall be measured, in mm, and the extent of above or below to a water pressure of 5 bars acting water permeation shall be established. normal to the mould- filling direction (Figures 2 and 3) for a period of three days. This pressure shall be kept Compressive Strength constant throughout the test. If water penetrates through Concrete cubes of 150 mm were used to determine to the underside of the specimen, the test may be the compressive strength. The samples were remolded

- 250 - Jordan Journal of Civil Engineering, Volume 5, No. 2, 2011

24 h after casting and cured in water until the testing The compressive strengths of concretes were ages. determined at the age of 28 days.

Figure 1: Particle size distribution

Figure 2: Testing water impermeability on sample 120 mm/200 mm/200 mm

RESULTS AND DISCUSSION slump values because of the spherical shaped particles which reduce the interparticle friction. The slump values Slump increased as super pozz ratio increased from 10% to The slump results are shown in Figure (6) for 20% and to 30%. High slag Portland cement mixtures ordinary Portland cement mixtures. The mixtures had almost equal slump values for each ratio of silica containing silica fume had the lowest slump. This is due fume, fly ash and super pozz. to high surface area of silica fume particles which have higher water demands than mixtures without silica Water Permeability of Concrete fume. The mixtures containing super pozz had higher The water permeability of concrete and the ratio of

- 251 - Influence of Silica Fume,… A. A. Elsayed permeability are given in Table (11) and Figure 4. The The mean of maximum depth of water penetration of ratio of permeability is defined as the permeability of 20% FA concrete had a lower average reduction of concrete containing pozzolanic materials divided by the 44% compared to the control mixture OPC. The mixture permeability of OPC concrete at the same age of testing.

Figure 3: Apparatus of permeability test

Figure 4: Results of maximum water penetration depth (mm)

- 252 - Jordan Journal of Civil Engineering, Volume 5, No. 2, 2011

Figure 5: Results of compressive strength (kg/cm2)

Figure 6: Results of slumps (mm) containing blast furnace slag had an average reduction silica fume. The mixture containing 10% SP had the of 7 % when compared to the control mixture. Mixture lowest water permeability value compared to those of of 10% SF had a lower value than that of the OPC with all mixtures. The average water penetration curves with a reduction of 66%. The fine size particles of silica different fly ash, super pozz and silica fume ratios are fume fill in the spaces between the cement particles, shown in Figures (7, 8 and 9), respectively. The making the concrete much denser than mixtures without comparison of the average water penetration curves

- 253 - Influence of Silica Fume,… A. A. Elsayed with best ratios of different admixtures is shown in Figure 10.

Figure 7: Average water penetration curves with different fly ash ratios

Figure 8: Average water penetration curves with different super pozz ratios

- 254 - Jordan Journal of Civil Engineering, Volume 5, No. 2, 2011

Figure 9: Average water penetration curves with different silica fume ratios

Figure 10: Comparison of the average water penetration curves with best ratios of different admixtures

Compressive Strength 465 kg/cm2. The concrete containing high slag cement Compressive strengths of concretes are compared to had the compressive strength of 517 kg/cm2 or 111% of that of OPC concrete in Table (11) and Figure 5. The the OPC. Compressive strength values of 10% FA, 20% compressive strength at 28 days of OPC concrete was FA and 30% FA concretes were 435, 414 and 370

- 255 - Influence of Silica Fume,… A. A. Elsayed kg/cm2 or 94%, 89% and 80% compared to OPC silica fume gave the smallest value of 12 mm water concrete, respectively. At a higher replacement ratio penetration. This ratio gave a reduction in (30% FA), the strength of concrete became lower, since permeability of 56% and an increase in compressive the amount of Portland cement was greatly reduced. For strength of 32%. the series of SP concretes, the compressive strength 4. The ratio of 20% replacement of cement weight of values were 486,422 and 386 kg/cm2or 105%, 91% and fly ash gave the smallest value of 14 mm water 83% compared to those of the OPC concrete, for10% penetration for high slag cement. This ratio gave a SP, 20% SP and 30%SP concretes, respectively. Again, reduction in permeability of 48% and an increase in increasing the replacement ratio of SP, the compressive compressive strength of 6%. strength of concrete was reduced, but was still slightly 5. The ratio of 30% replacement of cement weight of higher than that of FA concretes. For the series of SF super pozz gave the smallest value of 19 mm water concretes, the compressive strength values were penetration for high slag cement. This ratio gave a 504,643 and 533 kg/cm2 or 108%, 133% and 115% reduction in permeability of 30% and an increase in compared to those of the OPC concrete, for 5% SF,10% compressive strength of 4.8%. SF and %15 SF concretes, respectively. 10% SF had 6. The ratio of 15% replacement of cement weight of higher compressive strength values because silica fume silica fume gave the smallest value of 14 mm water is much finer than super pozz. As a result of the higher penetration for high slag portland cement. This ratio surface area, the pozzolanic reaction proceeds rapidly gave a reduction in permeability of 56% and an and strength is quickly developed. increase in compressive strength of 25%. 7. Silica fume concretes have higher compressive CONCLUSIONS strength at all cement replacement levels and tend to give lower permeability values. 1. The results insure the effectiveness of minerals' 8. The optimum cement replacement by fly ash, super admixtures as fly ash, super pozz and silica fume to pozz and silica fume in this research was 10% super improve properties of concrete, to reduce pozz. Higher replacement gave higher permeability permeability and to increase the resistance. of concrete and lower compressive strength. 2. The ratio of 10% replacement of cement weight of 9. The permeability of super pozz, fly ash and silica super pozz gave the smallest value of 10 mm water fume concretes depends on the cement replacement penetration. This ratio gave a reduction in ratio. In general, the permeability of concrete permeability of 63% and an increase in compressive reduces with the increase in the compressive strength of 7.6%. strength of concrete. 3. The ratio of 10% replacement of cement weight of

REFERENCES Natural Pozzolan for the Use as a Mineral Admixture in Portland Cement Concrete. Designation C 618. Alexander, M.G. and Magee, B.J. 1999. Durability Philadelphia. Performance of Concrete Containing Condensed Silica Benz, Dale, Edward, P. and Garboczi, J. 1991. Simulation Fume, Cement Concrete Res., 29 (6): 917-922. Studies of the Effects of Mineral Admixtures on the ASTM C 618. American Society for Testing and Materials. Cement Past Aggregate Interfacial Zone, ACI Materials ASTM Specification for Fly Ash and Raw or Calcined Journal (American Concrete Institute), September-

- 256 - Jordan Journal of Civil Engineering, Volume 5, No. 2, 2011

October, 88 (5): 518-529. Concrete, (ACI 212.1R-81), Concrete International: Fulton, F.S. 1974. The Properties of Portland Cements Design and Construction, May, 27 (5): 64-65. Containing Milled Granulated Blast-furnace Slag, Marsh, B.K., Day, R.L. and Bonner, D.G. 1985. Pore Portland Cement Institute Monograph, The Portland Structure Characteristics Affecting the Permeability of Cement Institute, Johannesburg, South Africa. Cement Paste Containing Fly Ash. Cement Concrete Garbczi, Edward J. 1990. Permeability, Diffusivity and Res., 15 (6):1027-1038. Microstructural Parameters. A Critical Review, Cement Mehta, P. Kumar. 1993. Concrete Structure, Properties and and Concrete Research, 20 (4): 591-601. Materials, Prentice- Hall, Inc., Englewood Cliffs, N.J. Helmuth, R. A. 1987. Fly Ash in Cement and Concrete, 07632. SP040T, Portland Cement Association, Skokie, IL. Mindess, Sidney and Young J. Francis. Concrete, P 24. Klieger, Paul and Joseph F. Lamond (Eds.). 1994. Prentice Hall, Inc., Englewood Cliffs, New Jersey, Significance of Tests and Properties of Concrete and 07632. Concrete-Making Materials, ASTM STP 169C. Song, P.S. and Hwang, S. 2004. Mechanical Properties of Konstantin G. Sobolev and Vladimir G. Batrakov. 2007. High Strength Steel Fiber-Reinforced Concrete, Journal of Materials in Civil Engineering © ASCE, Construction and Building Materials, November, 18 October 2007 / 812. (9): 669-673. Lewis, D. W. 1985. Discussion of Admixtures for

- 257 -